Type carrier assembly

ABSTRACT

An assembly for moving a train of print slugs having type characters thereon in a continuous path and along the print line of a high speed, on-the-fly, impact printer. Each print slug has a single tooth and the slugs are driven by a gear whose teeth mesh with the teeth of the slugs. The slugs are guided along their path in a track which slidably engages top and bottom portions of the slugs. The tooth of each slug is located between its top and bottom portions and the gear engages the slugs&#39;&#39; teeth at locations equidistant from where the track engages the slugs so that a vertical overturning moment is not imparted to the slugs by the gear. Additionally, the type characters are centrally located between the slugs&#39;&#39; top and bottom portions so that impact of the printer&#39;&#39;s hammers at the print line does not produce vertical overturning moments on the slugs. Further, the slugs abut as they travel around the gear and remain in abuttment throughout their entire path so that adjacent slugs always move at the same velocity and a stable train is provided.

aet 1 Benson et a1.

[ June 26, 1973 TYPE CARRIER ASSEMBLY [73] Assignee: Mohawk Data Sciences Corporation,

Herkimer, NY.

[22] Filed: Dec. 30, 1970 [21] Appl. No.: 102,731

[52] US. Cl. 101/93 C, 101/111 [51] Int. Cl. B4lj 1/02, B4lj 1/20 [58] Field of Search 101/111, 93 C, 109

[5 6] References Cited I UNITED STATES PATENTS 3,633,501 1/1972 Edwards 101/111 3,630,144 12/1971 Hillpert 101/1 11 3,379,126 4/1968 Staller et al..... 101/93 C X 3,224,366 12/1965 Cunningham 101/111 X 3,577,913 5/1971 Hinze 101/93 C 3,399,619 9/1968 Sims 101/93 C 3,435,756 4/1969 Martin 101/111 X 3,467,234 9/1969 Potter et a1. 101/93 C X 3,012,499 12/1961 Amada 101/111 X 3,621,778 11/1971 Ripple et a1 101/93 c Primary ExaminerRobert E. Pulfrey Assistant Examiner-E. M. Coven Attorney-Francis J. Thomas, Richard H. Smith, Thomas C. Siekman and Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT An assembly for moving a train of print slugs having type characters thereon in a continuous path and along the print line of a high speed, on-the-fly, impact printer. Each print slug has a single tooth and the slugs are driven by a gear whose teeth mesh with the teeth of the slugs. The slugs are guided along their path in a track which slidably engages top and bottom portions of the slugs. The tooth of each slug is located between its top and bottom portions and the gear engages the slugs teeth at locations equidistant from where the track engages the slugs so that a vertical overturning moment is not imparted to the slugs by the gear. Additionally, the type characters are centrally located between the slugs top and bottom portions so that impact of the printers hammers at the print line does not produce vertical overturning moments on the slugs. Further, the slugs abut as they travel around the gear and remain in abuttment throughout their entire path so that adjacent slugs always move at the same velocity and a stable train is provided.

4 Claims, 9 Drawing Figures 1 TYPE CARRIER ASSEMBLY BACKGROUND OF THE INVENTION This invention relates to high speed printers and, more particularly, to a type carrier assembly for such a printer.

It is well known in the high speed printing art to print a document by selectively striking it against type characters on a moving type carrier assembly placed in back of the document. Several forms of type carrier assemblies have been employed with this on-the-fly method of printing. The oldest form is the print drum. With drum printers, individually operable print hammers arranged along the line to be printed are associated with a constantly rotating type drum having engraved about its periphery columns of the various type characters used. Each column of type characters is aligned to cooperate with one of the hammers which strikes the document against selected characters in that column as the drum rotates in a direction perpendicular to the line being printed.

Another form of type carrier assembly for on-the-fly printing is the so-called chain. A chain printer utilizes a constantly moving endless chain which has the type characters thereon and is moved past the hammers in a direction parallel to the line being printed. The chain type carrier assembly is generally made up of a plurality of print slugs secured to an endless flexible belt which moves in a continuous path, part of which is along the print line adjacent the hammers where printing occurs. Generally, the chain moves around spaced-apart driving and idler gears which engage the belt and are located at opposite ends of the print line.

The most frequently cited advantage of the chain assembly over the drum is that the unavoidable slight inaccuracies which occur in the timing of the hammers cause the character images printed on the document to be misplaced slightly in a horizontal rather than a vertical direction as is the case with the drum. The result is that the chain assembly produces a much more pleasing aesthetic appearance and is easier to read.

However, the chain form of type carrier assembly has its own disadvantages. The inherent flexibility of the belt contributes to errors in slug spacing and thus obviously impairs the precision with which the hammers strike the slugs at the print line. In addition, the belt may be unable to withstand the loads applied to it when the chain is rapidly moved for printing at very high speeds.

These problems of the chain are obviated by a third form of type carrier assembly the train of print slugs. Train printers are substantially identical to the chain variety except that a belt is not used and the slugs are driven by and engage the gears directly. The slugs travel in an abutting relationship along the print line and in an endless path. Since the train moves in the same path as the chain, it has the chains advantages. However, in train printers, the slugs are pushed along their path at the print line and thus must remain in contact with each other. Errors in slug spacing at the print line are thereby avoided.

One such train type carrier assembly is disclosed by U. S. Pat. No. 3,224,366 issued to J. M. Cunningham. However, the type carrier disclosed in this patent utilizes a rather complicated and expensive form of slugs. Each slug has a plurality of teeth located at its top which are engaged by the gears to move the train. Since the slugs are driven from their top, some means is obviously necessary to countervail the vertical overturning moment applied to them when they are engaged by the I gears. Also, the type characters are located at the bottom of the slugs so that another vertical overturning moment is applied to the slugs as they are impacted by the printers hammers along the print line. The features which must be added to counter these over-turning moments obviously must increase the cost and complexity of the printer. In addition, the slugs do not abut when they are engaged by the gears because of the particular arrangement between the gears teeth and the teeth of the slugs. Since the slugs must abut as they travel between gears, they necessarily must accelerate and decelerate as they leave and enter the gears. Thus, adjacent slugs leaving and entering the gears move at different velocities and do not abut; the train assembly is unstable to this extent.

SUMMARY OF THE INVENTION It is, therefore, the primary object of this invention to provide a type carrier assembly having a stable train of print slugs which is easy to manufacture and maintain and wherein the print slugs precisely and smoothly move along their path.

According to the invention, these objects and others are achieved by a type carrier assembly having a train of print slugs, each of which contains a single tooth. A gear having teeth adapted to mesh with the teeth of the slugs is provided to drive the slugs and a track is provided to guide the slugs along their endless path. The track slidably engages top and bottom portions of the slugs while the tooth of each slug is located between its top and bottom portions. Preferably, the track engages the slugs at locations equidistant from where the gear engages and drives the slugs so that the slugs are not subject to a vertical over-turning moment applied by the gear. Additionally, preferably, the teeth of the gear and the teeth of the slugs are arranged such that adjacent slugs abut when being driven around the gear so that the slugs abut and travel at the same velocity throughout their entire path, including those locations where they enter and leave the gear. And, also preferably, the type characters are centrally located between the top and bottom portions of the slugs so that a vertical overturning moment is not applied to the slugs by print hammer impact.

The assembly preferably is embodied in a selfcontained unit where the driving gear is mounted at one end of an elongated center member. An idler gear is mounted at the center members opposite end and the train of slugs move around the two gears and along the sides of the center member guided within the track. At those locations where the slugs move from a gear to the sides of the center member, ramps are provided to help guide the slugs should they deviate from their proper path. In a second embodiment of the invention, only the driving gear is employed and the opposite end of the center member'is convex with the slugs being guided around it by the track.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevation view, partly in section, of a preferred embodiment of type carrier assembly according to the invention.

FIG. 2 is a partial top view of the type carrier assembly shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a type carrier assembly having a train of abutting side-by-side print slugs 2 with type characters 4 thereon. Each individual print slug has two type characters arranged beside each other. The train of print slugs is driven in an endless path along the side of the assembly shown in FIG. 2 and around the assemblys curved ends, 6 and 8, which house driving and idler gears. 7

As illustrated in FIG. 2, the train of print slugs is driven so as to continually present one or more fonts of the type characters to a bank of selectively operated hammers l0 (schematically illustrated) which are arranged along a printers print line (the line along which characters are printed). The printer is of the on-the-tly, impact variety so that when printing a line, the proper hammers are operated to selectively impact an inked ribbon l2 and the document 14 being printed upon against selected type characters 4 on the print slugs 2 (FIG. 1) as the slugs move along the print line.

As shown in FIG. 1, the driving gear housed in the assemblys end 6 is itself driven via a gear 16 driven by pinion 18 mounted on a rotating shaft 20. When the driving gear is rotated, it engages the train and pushes the abutting print slugs around the end 6 of the assembly housing the driving gear, along the print line at the straight front side of the assembly, around the idler end 8 of the assembly shown in FIG. 1 and, thereafter, along the straight backside of the assembly shown in FIG. 1. The top view of the driving end 6 is similar to the idler end 8 shown in FIG. 1. The type carrier assembly is a self-contained unit and mounted on the printer by a plurality of appropriately located screws 24, only one of which is illustrated.

FIG. 3 is a section through the straight portion of the type carrier assembly shown in FIG. 2. The assembly includes an elongated top plate 26 and an elongated bottom plate 28. Front and back elongated side members 42 and 40 are located between these two plates, disposed toward the front and back, respectively, of the assembly. These four elements (26, 28, 42, 40) are held together by appropriately placed cap screws 44 located in recesses 45, some of which are illustrated in FIGS. 1 and 2. Upper and lower rails are mounted at the sides of plates 26 and 28. As shown in FIG. 3, the front side of the type carrier assembly has upper and lower rails 30 and 32 mounted thereon adjacent but spaced from the side member 42. Similarly, at the back side of the type carrier assembly adjacent and spaced from the side member 40, upper and lower rails 34 and 36 are mounted to the sides of the top and bottom plates. The rails and top and bottom plates are joined by cap screws 38 located in recesses 39 as illustrated in FIGS. 1, 2 and 3.

As shown in FIG. 3, an elongated opening is formed by these members at each side of the type carrier assembly. The opening is formed between a pair of upper and lower rails, between the top and bottom plates and one of the side members, 40 or 42. The opening is T- shaped in cross-section and extends along both the front and back sides of the assembly. The inside surfaces of the opening are parallel and flat and the elongated opening at the front side of the type carrier assembly extends parallel to and along the print line.

As also shown in FIG. 3, the print slugs 2 are approximately T-shaped and closely fit in the elongated T- shaped openings provided at the front and back sides of the type carrier assembly. The rails, plates and side members thus form part of a track to accurately guide the train of slugs around the assembly. The type characters 4 on the print slugs 2 are exposed so that they may be impacted by the hammers 10 at the print line.

FIG. 4 is a sectional view illustrating the type carrier assembly at its end which houses the driving gear. The idler end is shown at the left part of FIG. 1 and is substantially identical. Each end of the assembly contains upper and lower end plates, 52 and 54. Each end plate has a lip (52a and 54a) which functions similar to a rail (30, 32, 34 and 36) at the sides of the type carrier assembly. Both the idler and driving ends are semicircular. Their lips follow a semi-circular path and meet with the rails at the straight sides of the assembly. In effeet, the lips are merely curved extensions of the rails and connect the rails on opposite sides of the assembly with each other. Additionally, the upper and lower end plates (52, 54) are merely extensions of the top and bottom plates (26, 28) at the straight portion of the assembly. Thus, these members at the ends of the assembly (52, 54, 52a, 54a) form additional parts of a track to guide the slugs at the assemblys ends and a complete track is provided to guide the slugs in a continuous path along both sides and around both ends of the assembly.

As shown in FIG. 2, the upper and lower end plates 52, 54 are connected to the side members 42, 40 by fasteners 60 located in recesses 61. Each gear is rotatably mounted to one of the upper end plates 52 as shown in FIGS. 1 and 4. A circular hole through which fasteners 58 project is provided in the upper end plate 52 at each end of the type carrier assembly. The fasteners clamp the upper end plates 52 between top caps 56 and flanges 57 having holes into which the fasteners thread. The flanges are connected to stationary shafts 50 on which the idler gear 46 (FIG. 1) and driving gear 47 (FIG. 4) are rotatably mounted by bearings 48. In this manner, the gears are mounted in and made part of the assembly. As further shown in FIGS. 1 and 4, the driving gear has an extension 22 which is connected to gear 16 for rotation. The idler gear 46, shown in FIG. 1 is substantially identical to the driving gear shown in FIG. 4 but is freely rotatable. The driving gear engages the print slugs to push them around the assembly and across the print line. However, the idler gear arrangement serves to help guide the print slugs around the end 8 of the assembly at which it is located.

One of the print slugs 2 is illustrated in FIGS. 6 and 6a. FIG. 6A is a side view of the slug which for ease of description is divided into three portions by lines A--A and 88. Those portions above line A-A and below line B-B may be termed top and bottom portions, re-

spectively, of the slug while that portion between lines A-A and B-B may be termed the slugs middle portion. The front surface of the slug contains the type characters 4 thereon. More exactly, the type characters are located on the front surface 63a of the slugs middle portion. The top and bottom portions are ears projecting from the back of the slugs middle portion. The back surfaces of the top and bottom portions, 60b and 62b, lie in a common plane and a central recess 63b in the back surface of the middle portion of the slug is located between them. As shown in FIG. 3, back surfaces (60b and 62b) of the top and bottom portions ride along members 40 and 42 when the slugs move along the straight sides of the assembly. The front surface of the top and bottom portions of the slugs ride along the inside surfaces of the rails (30, 32, 34, 36) as shown in FIG. 3. Thus, the slugs are effectively guided along the track at the straight sides of the assembly by their top a and bottom portions. The rails maintain surfaces 60b and 62b adjacent the side members 40, 42.

When a slug is impacted at the print line by a hammer (FIG. 2), the back surfaces (60b, 62b) of its top and bottom portions are pushed perpendicularly against the front elongated member 42 which thereby serves as an anvil. As shown in FIG. 6A, the type characters 4 are located centrally between and equidistant from surfaces 60b and 62b. This allows the characters on the slugs to be struck by the hammers without any vertical overturning moment being imparted to the slugs.

Referring to FIGS. 4 and 6A, when the slugs are engaged by the driving and idler gears, the gears teeth project into the recesses 63b in the rear surfaces of the middle portions of the slugs. Each slug has a single tooth 2a within its recess which meshes with the teeth of the gears. The tooth is slightly spaced inwardly with respect to the back surfaces (60b, 62b) of the top and bottom portions so that the tooth does not contact the side members, 40 and 42, when moving around the assembly.

Referring to FIG. 4, the slugs are guided at the ends of the assembly while engaged by the gears in a manner similar to the manner in which they are guided along the straight sides of the assembly. The front surfaces (60a and 62a) of the slugs top and bottom portions slide along the lips, 52a and 54a, of the upper and lower end plates. The tooth 2a and the recess 63b is centrally located in each slug and placed equidistant from where the top and bottom portions front surfaces, 60a and 62a, slide along the lips. Thus, the driving and idler gears centrally engage the slugs without applying vertical overturning moments to them.

FIG. 5 is a top sectional view of the driving gear 47 and the .train of slugs as they are engaged by the gear.

As indicated by the arrow in FIG. 5, the gears rotate counterclockwise to move the train. The tooth 2a on each slug is disposed toward its side which trails as the train moves around the assembly. The gear 47 has teeth 49 which project into the recesses 63b (FIG. 6A) in the slugs and between the teeth of adjacent slugs in the train. To allow the slugs to abut as they travel around the gears, the teeth 49 of the gears do not tightly mesh with the teeth 2a of the slugs. Since the gear teeth push on the trailing side of each slug tooth a gap 72 appears between the leading side of each slug tooth and the trailing side of a gear tooth. One of the features of the type carrier assembly is to provide slugs which are easily manufactured and, thus, inexpensive. With the tooth of each slug disposed toward its side that trails in the train, the trailing side of the slugs tooth is easily accessed and may be manufactured to close tolerances. Because it is against this side of the tooth that the gear pushes, the formation of this side of the tooth is most critical. The other side of each slugs tooth 2a is not as easily accessed but manufacturing tolerances are not as critical here since a gap 72 will necessarily occur adjacent this side of the tooth 2a. The slugs may be easily manufactured by being initially cast with the trailing sides of their teeth machines to close tolerances thereafter.

As also illustrated in FIG. 5, adjacent slugs in the train abut as they travel around the ends of the assembly and are engaged by the gears. The teeth of the gears and teeth of the slugs are adapted to mesh with each other in a manner to achieve this. The abutting surfaces of the slugs are located on lines CC and DD shown in FIG. 6. Since these surfaces are located on the innermost portion of each slug as it moves around the gears, they must taper inwardly as shown. Referring to FIG. 5, these lines CC and DD are along radii of the circular idler and driving gears (which have equal diameters) when they are engaging the slugs.

Thus, theslugs abut as they travel around the ends of the assembly engaged by the gears and this abuttment occurs along the surfaces defined by the CC and DD lines in FIG. 6. Inherently, the slugs must abut as they travel along the straight sides of the assembly and, as illustrated in FIGS. 1 and 6, this abuttment occurs along the parallel sides of the slugs. As shown in FIG. 6, those locations designated Y and Z on each slug always remain in abuttment with the adjacent slugs whether the slug is at a side or an end of the assembly since the Y and Z locations are those points where the slugs parallel side surfaces meet the surfaces on the CC and DD lines. Therefore, the slugs in the train always abut and there is never a difference in the velocity of adjacent slugs. A solid and stable train of slugs is provided.

Referring back to FIGS. 2 and 4, each end of each side member 40, 42 has two fingers which extend above and below a gear. The fingers at that end of side member 42 which are adjacent the driving gear are shown in FIG. 4 and designated 42a and 42b. FIG. 1 shows the fingers 42c and 40c which extend above the idler gear from side members 42 and 40 respectively. The fingers are all similar and located where the slugs travel either from around a gear to the straight side of the type carrier assembly or from the straight side to a gear. At the former locations, the fingers (e.g., 40c in FIG. 2) are so shaped to allow them to act as ramps for guiding the slugs should they deviate from their correct path as they enter the rails. The shape of those fingers at the latter locations (e.g., 420 in FIG. 2) is unimportant since the slugs cannot possibly deviate from their proper path as they enter the gears; however, for ease of manufacturing, similarly shaped fingers are used at both ends of the side members 40, 42.

FIGS. 7 and 8 disclose a second embodiment of the invention. The type carrier assembly disclosed in these two Figures is the same as the preferred embodiment disclosed above except that an idler gear assembly is not utilized to guide the slugs around the end of the assembly opposite to the driving gear. At this end, an end member 74 is provided between the upper and lower (52 and 54) end plates of the assembly. This end member is connected to the elongated side members 40 and 42 as shown in FIG. 7 and shaped to provide a circular convex surface along which the rear surfaces of the slugs top and bottom portions, 60b and 621) (FIG. 6a), may slide. The circular surface is contiguous with the outside surfaces of the elongated members 40 and 42 and, along with lips 52a, 54a and end plates 52, 54, forms a track to guide the slugs around the end of the assembly without an idler gear arrangement.

Thus, it may be seen that both embodiments of the type carrier assembly disclosed provide. type slugs which are easily manufactured. In addition, no vertical overturning moments are applied to the slugs of the train as they are driven by the driving gear and impacted by the hammers at the print line. A stable train is provided with adjacent slugs always abutting at the same points whether at the gears or straight sides of the assembly. The danger of the slugs deviating from their path as they leave the circular end portion of the assembly and enter the straight portion is obviated by the appropriately placed ramp surfaces on the side members.

It will be appreciated that various changes in the form and details of the above described preferred embodiments may be effected by persons of ordinary skill without departing from the true spirit and scope of the invention.

We claim:

1. In a type carrier assembly for a high-speed on-thefly printer, the combination comprising:

guide means defining a closed type path having at least one straightaway;

a spur gear rotatably mounted adjacent said path and arranged such that the teeth thereof pass through an arc which is parallel to a segment of said type path, the contact surfaces of said teeth being of convex curvature;

a plurality of type bearing slugs adapted to travel within said guide means along said type path, each said slug having a substantially planar tooth surface adapted to engage the contact surface of one of said gear teeth along a contact line, the locus of said contact lines defining a segment of a cylinder concentric about the axis of said gear, the length of each said slug, measured in the direction of slug travel, being substantially equal to the straight-line distance between the contact surfaces of two adjacent gear teeth as measured from the respective contact lines thereon, said slugs further having front and rear end portions each of which includes a first planar end surface and a second planar end surface, said end surfaces intersecting along a line lying in said locus cylinder; and means for driving said gear to push said slugs in abutting contact with one another around said type path, said first planar end surfaces of adjacent slugs being arranged for surface abutment with one another when said slugs traverse said straightaway and said second planar end surfaces of adjacent slugs being arranged for surface abutment with one another when said slugs engage said spur gear. 2. The type carrier assembly set forth in claim 1 wherein said type path lies in a plane bisecting said spur gear in a direction perpendicular to the axis thereof and wherein each said slug is symmetrical, both in profile and in mass, about said plane.

3. The type carrier assembly set forth in claim 2 wherein the types carried by each said slug are centered on a planar type face which is located on said slug perpendicular to and symmetrical about the face of said type path and parallel to the direction of slug movement.

4. The type carrier assembly set forth in claim 3 wherein said guide means comprises:

a pair of mirror image, continuous guide rails shaped to conform to said type path;

means for mounting said guide rails at equal distances above and below the plane of said type path; and

backup guide surface means perpendicular to the plane of said type path and positioned inside of said guide rails such that said slugs are constrained to slide within said guide means with said typeface positioned between said guide rails and with a surface opposite said typeface bearing against said backup guide surface means.

i 1 l l 

1. In a type carrier assembly for a high-speed on-the-fly printer, the combination comprising: guide means defining a closed type path having at least one straightaway; a spur gear rotatably mounted adjacent said path and arranged such that the teeth thereof pass through an arc which is parallel to a segment of said type path, the contact surfaces of said teeth being of convex curvature; a plurality of type bearing slugs adapted to travel within said guide means along said type path, each said slug having a substantially planar tooth surface adapted to engage the contact surface of one of said gear teeth along a contact line, the locus of said contact lines defining a segment of a cylinder concentric about the axis of said gear, the length of each said slug, measured in the direction of slug travel, being substantially equal to the straight-line distance between the contact surfaces of two adjacent gear teeth as measured from the respective contact lines thereon, said slugs further having front and rear end portions each of which includes a first planar end surface and a second planar end surface, said end surfaces intersecting along a line lying in said locus cylinder; and means for driving said gear to push said slugs in abutting contact with one another around said type path, said first planar end surfaces of adjacent slugs being arranged for surface abutment with one another when said slugs traverse said straightaway and said second planar end surfaces of adjacent slugs being arranged for surface abutment with one another when said slugs engage said spur gear.
 2. The type carrier assembly set forth in claim 1 wherein said type path lies in a plane bisecting said spur gear in a direction perpendicular to the axis thereof and wherein each said slug is symmetrical, both in profile and in mass, about said plane.
 3. The type carrier assembly set forth in claim 2 wherein the types carried by each said slug are centered on a planar type face which is located on said slug perpendicular to and symmetrical about the face of said type path and parallel to the direction of slug movement.
 4. The type carrier assembly set forth in claim 3 wherein said guide means comprises: a pair of mirror image, continuous guide rails shaped to conform to said type path; means for mounting said guide rails at equal distances above and below the plane of said type path; and backup guide surface means perpendicular to the plane of said type path and positioned inside of said guide rails such that said slugs are constrained to slide within said guide means with said typeface positioned between said guide rails and with a surface opposite said typeface bearing against said backup guide surface means. 